diff --git a/book.py b/book.py
index 2adfb4f..a9a2add 100644
--- a/book.py
+++ b/book.py
@@ -3,7 +3,7 @@
 # The COPYRIGHT file at the top level of this repository contains the
 # full copyright notices and license terms.
 
-from trytond.model import Workflow, ModelView, ModelSQL, fields, Check
+from trytond.model import Workflow, ModelView, ModelSQL, fields, Check, tree
 from trytond.pyson import Eval, Or, Bool, Id
 from trytond.exceptions import UserError
 from trytond.i18n import gettext
@@ -20,6 +20,16 @@ STATES = {
     }
 DEPENDS=['state']
 
+# states in case of 'btype'!=None
+STATES2 = {
+    'readonly': Or(
+            Eval('state', '') != 'open',
+            ~Bool(Eval('btype')),
+        ),
+    'invisible': ~Bool(Eval('btype')),
+    }
+DEPENDS2 = ['state', 'btype']
+
 sel_state_book = [
     ('open', 'Open'),
     ('closed', 'Closed'),
@@ -27,7 +37,7 @@ sel_state_book = [
     ]
 
 
-class Book(Workflow, ModelSQL, ModelView):
+class Book(tree(separator='/'), Workflow, ModelSQL, ModelView):
     'Cashbook'
     __name__ = 'cashbook.book'
 
@@ -35,9 +45,15 @@ class Book(Workflow, ModelSQL, ModelView):
         required=True, ondelete="RESTRICT")
     name = fields.Char(string='Name', required=True,
         states=STATES, depends=DEPENDS)
-    btype = fields.Many2One(string='Type', required=True,
+    btype = fields.Many2One(string='Type',
+        help='A cash book with type can contain postings. Without type is a view.',
         model_name='cashbook.type', ondelete='RESTRICT',
-        states=STATES, depends=DEPENDS)
+        states={
+            'readonly': Or(
+                    STATES['readonly'],
+                    Bool(Eval('lines')),
+                ),
+        }, depends=DEPENDS+['lines'])
     owner = fields.Many2One(string='Owner', required=True, select=True,
         model_name='res.user', ondelete='SET NULL',
         states=STATES, depends=DEPENDS)
@@ -54,8 +70,8 @@ class Book(Workflow, ModelSQL, ModelView):
         states=STATES, depends=DEPENDS)
     reconciliations = fields.One2Many(string='Reconciliations',
         field='cashbook', model_name='cashbook.recon',
-        states=STATES, depends=DEPENDS)
-    number_sequ = fields.Many2One(string='Line numbering', required=True,
+        states=STATES2, depends=DEPENDS2)
+    number_sequ = fields.Many2One(string='Line numbering',
         help='Number sequence for numbering of the cash book lines.',
         model_name='ir.sequence',
         domain=[
@@ -65,41 +81,56 @@ class Book(Workflow, ModelSQL, ModelView):
                 ('company', '=', Eval('company', -1)),
                 ],
             ],
-        states=STATES, depends=DEPENDS+['company'])
+        states={
+            'readonly': STATES2['readonly'],
+            'required': Bool(Eval('btype')),
+        }, depends=DEPENDS2+['company'])
     number_atcheck = fields.Boolean(string="number when 'Checking'",
-        help="The numbering of the lines is done in the step Check. If the check mark is inactive, this happens with Done.")
-    start_date = fields.Date(string='Initial Date', required=True,
+        help="The numbering of the lines is done in the step Check. If the check mark is inactive, this happens with Done.",
+        states=STATES2, depends=DEPENDS2)
+    start_date = fields.Date(string='Initial Date',
         states={
             'readonly': Or(
-                STATES['readonly'],
+                STATES2['readonly'],
                 Bool(Eval('lines')),
                 ),
-        }, depends=DEPENDS+['lines'])
-    start_balance = fields.Numeric(string='Initial Amount', required=True,
-        digits=(16, Eval('currency_digits', 2)),
-        states={
-            'readonly': Or(
-                STATES['readonly'],
-                Bool(Eval('lines')),
-                ),
-        }, depends=DEPENDS+['lines', 'currency_digits'])
+            'invisible': STATES2['invisible'],
+            'required': Bool(Eval('btype')),
+        }, depends=DEPENDS2+['lines'])
     balance = fields.Function(fields.Numeric(string='Balance', readonly=True,
         digits=(16, Eval('currency_digits', 2)),
         depends=['currency_digits']), 'on_change_with_balance')
-    currency = fields.Many2One(string='Currency', required=True,
+    currency = fields.Many2One(string='Currency',
         model_name='currency.currency',
         states={
             'readonly': Or(
-                STATES['readonly'],
+                STATES2['readonly'],
                 Bool(Eval('lines', [])),
                 ),
-        }, depends=DEPENDS+['lines'])
+            'invisible': STATES2['invisible'],
+            'required': Bool(Eval('btype')),
+        }, depends=DEPENDS2+['lines'])
     currency_digits = fields.Function(fields.Integer(string='Currency Digits',
         readonly=True), 'on_change_with_currency_digits')
     state = fields.Selection(string='State', required=True,
         readonly=True, selection=sel_state_book)
     state_string = state.translated('state')
 
+    parent = fields.Many2One(string="Parent",
+        model_name='cashbook.book', ondelete='RESTRICT',
+        left='left', right='right')
+    childs = fields.One2Many(string='Children', field='parent',
+        model_name='cashbook.book')
+    left = fields.Integer(string='Left', required=True, select=True)
+    right = fields.Integer(string='Right', required=True, select=True)
+
+    @classmethod
+    def __register__(cls, module_name):
+        super(Book, cls).__register__(module_name)
+
+        table = cls.__table_handler__(module_name)
+        table.drop_column('start_balance')
+
     @classmethod
     def __setup__(cls):
         super(Book, cls).__setup__()
@@ -131,16 +162,18 @@ class Book(Workflow, ModelSQL, ModelView):
                 },
             })
 
+    @staticmethod
+    def default_left():
+        return 0
+
+    @staticmethod
+    def default_right():
+        return 0
+
     @classmethod
     def default_number_atcheck(cls):
         return True
 
-    @classmethod
-    def default_start_balance(cls):
-        """ zero
-        """
-        return Decimal('0.0')
-
     @classmethod
     def default_currency(cls):
         """ currency of company
@@ -193,12 +226,15 @@ class Book(Workflow, ModelSQL, ModelView):
     def get_rec_name(self, name):
         """ name, balance, state
         """
-        return '%(name)s | %(balance)s %(symbol)s | %(state)s' % {
-            'name': self.name or '-',
-            'balance': Report.format_number(self.balance or 0.0, None),
-            'symbol': getattr(self.currency, 'symbol', '-'),
-            'state': self.state_string,
-            }
+        recname = super(Book, self).get_rec_name(name)
+        if self.btype:
+            return '%(name)s | %(balance)s %(symbol)s | %(state)s' % {
+                'name': recname or '-',
+                'balance': Report.format_number(self.balance or 0.0, None),
+                'symbol': getattr(self.currency, 'symbol', '-'),
+                'state': self.state_string,
+                }
+        return recname
 
     @fields.depends('currency')
     def on_change_with_currency_digits(self, name=None):
@@ -209,28 +245,36 @@ class Book(Workflow, ModelSQL, ModelView):
         else:
             return 2
 
-    @fields.depends('id', 'start_balance')
+    @fields.depends('id')
     def on_change_with_balance(self, name=None):
         """ compute balance
         """
-        Line = Pool().get('cashbook.line')
+        pool = Pool()
+        Book2 = pool.get('cashbook.book')
+        Line = pool.get('cashbook.line')
         tab_line = Line.__table__()
         cursor = Transaction().connection.cursor()
 
-        query = tab_line.select(
+        line_query = Line.search([
+                ('cashbook.id', 'in', Book2.search([
+                        ('parent', 'child_of', [self.id]),
+                    ], query=True)),
+            ], query=True)
+
+        query = line_query.join(tab_line,
+                condition=tab_line.id==line_query.id,
+            ).select(
                 Sum(tab_line.credit - tab_line.debit).as_('balance'),
-                group_by=[tab_line.cashbook],
-                where=tab_line.cashbook == self.id
             )
 
         if self.id:
-            if self.start_balance is not None:
-                balance = self.start_balance
-                cursor.execute(*query)
-                result = cursor.fetchone()
-                if result:
+            balance = Decimal('0.0')
+            cursor.execute(*query)
+            result = cursor.fetchone()
+            if result:
+                if result[0] is not None:
                     balance += result[0]
-                return balance
+            return balance
 
     @classmethod
     @ModelView.button
@@ -263,12 +307,6 @@ class Book(Workflow, ModelSQL, ModelView):
         actions = iter(args)
         for books, values in zip(actions, actions):
             for book in books:
-                if 'start_balance' in values.keys():
-                    if len(book.lines) > 0:
-                        raise UserError(gettext(
-                            'cashbook.msg_book_err_startamount_with_lines',
-                            bookname = book.rec_name,
-                            ))
                 if book.state != 'open':
                     # allow state-update, if its the only action
                     if not (('state' in values.keys()) and (len(values.keys()) == 1)):
diff --git a/book.xml b/book.xml
index 465bcaf..810cf96 100644
--- a/book.xml
+++ b/book.xml
@@ -12,6 +12,13 @@ full copyright notices and license terms. -->
             <field name="priority" eval="10"/>
             <field name="name">book_list</field>
         </record>
+        <record model="ir.ui.view" id="book_view_tree">
+            <field name="model">cashbook.book</field>
+            <field name="type">tree</field>
+            <field name="priority" eval="10"/>
+            <field name="field_childs">childs</field>
+            <field name="name">book_tree</field>
+        </record>
         <record model="ir.ui.view" id="book_view_form">
             <field name="model">cashbook.book</field>
             <field name="type">form</field>
@@ -19,7 +26,7 @@ full copyright notices and license terms. -->
             <field name="name">book_form</field>
         </record>
 
-        <!-- action view-->
+        <!-- action view - list -->
         <record model="ir.action.act_window" id="act_book_view">
             <field name="name">Cashbook</field>
             <field name="res_model">cashbook.book</field>
@@ -35,6 +42,23 @@ full copyright notices and license terms. -->
             <field name="act_window" ref="act_book_view"/>
         </record>
 
+        <!-- action view - tree -->
+        <record model="ir.action.act_window" id="act_book_tree">
+            <field name="name">Cashbook</field>
+            <field name="res_model">cashbook.book</field>
+            <field name="domain" eval="[('parent', '=', None)]" pyson="1"/>
+        </record>
+        <record model="ir.action.act_window.view" id="act_book_tree-1">
+            <field name="sequence" eval="10"/>
+            <field name="view" ref="book_view_tree"/>
+            <field name="act_window" ref="act_book_tree"/>
+        </record>
+        <record model="ir.action.act_window.view" id="act_book_tree-2">
+            <field name="sequence" eval="20"/>
+            <field name="view" ref="book_view_form"/>
+            <field name="act_window" ref="act_book_tree"/>
+        </record>
+
         <!-- permission -->
         <!-- anon: deny all -->
         <record model="ir.model.access" id="access_book-anon">
@@ -251,18 +275,24 @@ full copyright notices and license terms. -->
             <field name="perm_read" eval="False"/>
             <field name="perm_write" eval="False"/>
         </record>
-        <record model="ir.model.field.access" id="fa_book-start_balance-anon">
-            <field name="field"
-                search="[('model.model', '=', 'cashbook.book'), ('name', '=', 'start_balance')]"/>
-            <field name="perm_read" eval="False"/>
-            <field name="perm_write" eval="False"/>
-        </record>
         <record model="ir.model.field.access" id="fa_book-currency-anon">
             <field name="field"
                 search="[('model.model', '=', 'cashbook.book'), ('name', '=', 'currency')]"/>
             <field name="perm_read" eval="False"/>
             <field name="perm_write" eval="False"/>
         </record>
+        <record model="ir.model.field.access" id="fa_book-parent-anon">
+            <field name="field"
+                search="[('model.model', '=', 'cashbook.book'), ('name', '=', 'parent')]"/>
+            <field name="perm_read" eval="False"/>
+            <field name="perm_write" eval="False"/>
+        </record>
+        <record model="ir.model.field.access" id="fa_book-childs-anon">
+            <field name="field"
+                search="[('model.model', '=', 'cashbook.book'), ('name', '=', 'childs')]"/>
+            <field name="perm_read" eval="False"/>
+            <field name="perm_write" eval="False"/>
+        </record>
 
         <!-- field-access - group_cashbook_admin -->
         <record model="ir.model.field.access" id="fa_book-company-group_cashbook_admin">
@@ -335,16 +365,23 @@ full copyright notices and license terms. -->
             <field name="perm_read" eval="True"/>
             <field name="perm_write" eval="True"/>
         </record>
-        <record model="ir.model.field.access" id="fa_book-start_balance-group_cashbook_admin">
+        <record model="ir.model.field.access" id="fa_book-currency-group_cashbook_admin">
             <field name="field"
-                search="[('model.model', '=', 'cashbook.book'), ('name', '=', 'start_balance')]"/>
+                search="[('model.model', '=', 'cashbook.book'), ('name', '=', 'currency')]"/>
             <field name="group" ref="group_cashbook_admin"/>
             <field name="perm_read" eval="True"/>
             <field name="perm_write" eval="True"/>
         </record>
-        <record model="ir.model.field.access" id="fa_book-currency-group_cashbook_admin">
+        <record model="ir.model.field.access" id="fa_book-parent-group_cashbook_admin">
             <field name="field"
-                search="[('model.model', '=', 'cashbook.book'), ('name', '=', 'currency')]"/>
+                search="[('model.model', '=', 'cashbook.book'), ('name', '=', 'parent')]"/>
+            <field name="group" ref="group_cashbook_admin"/>
+            <field name="perm_read" eval="True"/>
+            <field name="perm_write" eval="True"/>
+        </record>
+        <record model="ir.model.field.access" id="fa_book-childs-group_cashbook_admin">
+            <field name="field"
+                search="[('model.model', '=', 'cashbook.book'), ('name', '=', 'childs')]"/>
             <field name="group" ref="group_cashbook_admin"/>
             <field name="perm_read" eval="True"/>
             <field name="perm_write" eval="True"/>
@@ -421,16 +458,23 @@ full copyright notices and license terms. -->
             <field name="perm_read" eval="True"/>
             <field name="perm_write" eval="False"/>
         </record>
-        <record model="ir.model.field.access" id="fa_book-start_balance-group_cashbook">
+        <record model="ir.model.field.access" id="fa_book-currency-group_cashbook">
             <field name="field"
-                search="[('model.model', '=', 'cashbook.book'), ('name', '=', 'start_balance')]"/>
+                search="[('model.model', '=', 'cashbook.book'), ('name', '=', 'currency')]"/>
             <field name="group" ref="group_cashbook"/>
             <field name="perm_read" eval="True"/>
             <field name="perm_write" eval="False"/>
         </record>
-        <record model="ir.model.field.access" id="fa_book-currency-group_cashbook">
+        <record model="ir.model.field.access" id="fa_book-parent-group_cashbook">
             <field name="field"
-                search="[('model.model', '=', 'cashbook.book'), ('name', '=', 'currency')]"/>
+                search="[('model.model', '=', 'cashbook.book'), ('name', '=', 'parent')]"/>
+            <field name="group" ref="group_cashbook"/>
+            <field name="perm_read" eval="True"/>
+            <field name="perm_write" eval="False"/>
+        </record>
+        <record model="ir.model.field.access" id="fa_book-childs-group_cashbook">
+            <field name="field"
+                search="[('model.model', '=', 'cashbook.book'), ('name', '=', 'childs')]"/>
             <field name="group" ref="group_cashbook"/>
             <field name="perm_read" eval="True"/>
             <field name="perm_write" eval="False"/>
diff --git a/line.py b/line.py
index b708a5d..59b778f 100644
--- a/line.py
+++ b/line.py
@@ -51,7 +51,8 @@ class Line(Workflow, ModelSQL, ModelView):
     __name__ = 'cashbook.line'
 
     cashbook = fields.Many2One(string='Cashbook', required=True, select=True,
-        model_name='cashbook.book', ondelete='CASCADE', readonly=True)
+        model_name='cashbook.book', ondelete='CASCADE', readonly=True,
+        domain=[('btype', '!=', None)])
     date = fields.Date(string='Date', required=True, select=True,
         states=STATES, depends=DEPENDS)
     month = fields.Function(fields.Integer(string='Month', readonly=True),
@@ -607,8 +608,8 @@ class Line(Workflow, ModelSQL, ModelView):
             return 2
 
     @fields.depends('id', 'date', 'cashbook', \
-        '_parent_cashbook.start_balance', '_parent_cashbook.id',\
-        'reconciliation', '_parent_reconciliation.start_amount',
+        '_parent_cashbook.id', 'reconciliation', \
+        '_parent_reconciliation.start_amount',\
         '_parent_reconciliation.state')
     def on_change_with_balance(self, name=None):
         """ compute balance until current line, with current sort order,
@@ -646,7 +647,7 @@ class Line(Workflow, ModelSQL, ModelView):
             query = [
                 ('cashbook.id', '=', self.cashbook.id),
                 ]
-            balance = self.cashbook.start_balance
+            balance = Decimal('0.0')
 
             # get existing reconciliation, starting before current line
             # this will speed up calculation of by-line-balance
diff --git a/locale/de.po b/locale/de.po
index d1be018..6075046 100644
--- a/locale/de.po
+++ b/locale/de.po
@@ -70,10 +70,6 @@ msgctxt "model:ir.message,text:msg_category_type_not_like_parent"
 msgid "The type of the current category '%(catname)s' must be equal to the type of the parent category '%(parentname)s'."
 msgstr "Der Typ der aktuellen Kategorie '%(catname)s' muß gleich dem Typ der übergeordneten Kategorie '%(parentname)s' sein."
 
-msgctxt "model:ir.message,text:msg_book_err_startamount_with_lines"
-msgid "The initial amount of the cash book '%(bookname)s' cannot be changed because it already contains bookings."
-msgstr "Der Anfangsbetrag des Kassenbuchs '%(bookname)s' kann nicht geändert werden, da es bereits Buchungen enthält."
-
 msgctxt "model:ir.message,text:msg_line_deny_recon_by_state"
 msgid "For reconciliation, the line '%(recname)s' must be in the status 'Check' or 'Done'."
 msgstr "Für die Abstimmung muss die Zeile '%(recname)s' im Status 'Prüfen' oder 'Fertig' sein."
@@ -258,6 +254,10 @@ msgctxt "model:ir.ui.menu,name:menu_booklist"
 msgid "Cashbook"
 msgstr "Kassenbuch"
 
+msgctxt "model:ir.ui.menu,name:menu_booktree"
+msgid "Cashbook"
+msgstr "Kassenbuch"
+
 msgctxt "model:ir.ui.menu,name:menu_open_lines"
 msgid "Open Cashbook"
 msgstr "Kassenbuch öffnen"
@@ -286,6 +286,10 @@ msgctxt "model:ir.action,name:act_book_view"
 msgid "Cashbook"
 msgstr "Kassenbuch"
 
+msgctxt "model:ir.action,name:act_book_tree"
+msgid "Cashbook"
+msgstr "Kassenbuch"
+
 msgctxt "model:ir.action,name:act_type_view"
 msgid "Cashbook Type"
 msgstr "Kassenbuchtyp"
@@ -418,6 +422,10 @@ msgctxt "view:cashbook.book:"
 msgid "General Information"
 msgstr "Allgemein"
 
+msgctxt "view:cashbook.book:"
+msgid "Amount and Numbering"
+msgstr "Betrag und Nummerierung"
+
 msgctxt "view:cashbook.book:"
 msgid "Balance"
 msgstr "Saldo"
@@ -434,6 +442,10 @@ msgctxt "field:cashbook.book,btype:"
 msgid "Type"
 msgstr "Typ"
 
+msgctxt "help:cashbook.book,btype:"
+msgid "A cash book with type can contain postings. Without type is a view."
+msgstr "Ein Kassenbuch mit Typ kann Buchungen enthalten. Ohne Typ ist eine Sicht."
+
 msgctxt "field:cashbook.book,state:"
 msgid "State"
 msgstr "Status"
@@ -482,10 +494,6 @@ msgctxt "field:cashbook.book,currency_digits:"
 msgid "Currency Digits"
 msgstr "Nachkommastellen Währung"
 
-msgctxt "field:cashbook.book,start_balance:"
-msgid "Initial Amount"
-msgstr "Anfangsbetrag"
-
 msgctxt "field:cashbook.book,start_date:"
 msgid "Initial Date"
 msgstr "Anfangsdatum"
@@ -518,6 +526,22 @@ msgctxt "help:cashbook.book,number_atcheck:"
 msgid "The numbering of the lines is done in the step Check. If the check mark is inactive, this happens with Done."
 msgstr "Die Nummerierung der Zeilen wird beim Schritt 'Prüfen' erledigt. Bei inaktivem Häkchen passiert dies erst bei 'Fertig'."
 
+msgctxt "field:cashbook.book,parent:"
+msgid "Parent"
+msgstr "Übergeordnet"
+
+msgctxt "field:cashbook.book,childs:"
+msgid "Children"
+msgstr "Untergeordnet"
+
+msgctxt "field:cashbook.book,left:"
+msgid "Left"
+msgstr "Links"
+
+msgctxt "field:cashbook.book,right:"
+msgid "Right"
+msgstr "Rechts"
+
 
 ##################
 # cashbook.split #
diff --git a/locale/en.po b/locale/en.po
index fdab81a..912ff90 100644
--- a/locale/en.po
+++ b/locale/en.po
@@ -66,10 +66,6 @@ msgctxt "model:ir.message,text:msg_category_type_not_like_parent"
 msgid "The type of the current category '%(catname)s' must be equal to the type of the parent category '%(parentname)s'."
 msgstr "The type of the current category '%(catname)s' must be equal to the type of the parent category '%(parentname)s'."
 
-msgctxt "model:ir.message,text:msg_book_err_startamount_with_lines"
-msgid "The initial amount of the cash book '%(bookname)s' cannot be changed because it already contains bookings."
-msgstr "The initial amount of the cash book '%(bookname)s' cannot be changed because it already contains bookings."
-
 msgctxt "model:ir.message,text:msg_line_deny_recon_by_state"
 msgid "For reconciliation, the line '%(recname)s' must be in the status 'Check' or 'Done'."
 msgstr "For reconciliation, the line '%(recname)s' must be in the status 'Check' or 'Done'."
@@ -242,6 +238,10 @@ msgctxt "model:ir.ui.menu,name:menu_booklist"
 msgid "Cashbook"
 msgstr "Cashbook"
 
+msgctxt "model:ir.ui.menu,name:menu_booktree"
+msgid "Cashbook"
+msgstr "Cashbook"
+
 msgctxt "model:ir.ui.menu,name:menu_open_lines"
 msgid "Open Cashbook"
 msgstr "Open Cashbook"
@@ -266,6 +266,10 @@ msgctxt "model:ir.action,name:act_book_view"
 msgid "Cashbook"
 msgstr "Cashbook"
 
+msgctxt "model:ir.action,name:act_book_tree"
+msgid "Cashbook"
+msgstr "Cashbook"
+
 msgctxt "model:ir.action,name:act_type_view"
 msgid "Cashbook Type"
 msgstr "Cashbook Type"
@@ -382,6 +386,10 @@ msgctxt "view:cashbook.book:"
 msgid "General Information"
 msgstr "General Information"
 
+msgctxt "view:cashbook.book:"
+msgid "Amount and Numbering"
+msgstr "Amount and Numbering"
+
 msgctxt "view:cashbook.book:"
 msgid "Balance"
 msgstr "Balance"
@@ -398,6 +406,10 @@ msgctxt "field:cashbook.book,btype:"
 msgid "Type"
 msgstr "Type"
 
+msgctxt "help:cashbook.book,btype:"
+msgid "A cash book with type can contain postings. Without type is a view."
+msgstr "A cash book with type can contain postings. Without type is a view."
+
 msgctxt "field:cashbook.book,state:"
 msgid "State"
 msgstr "State"
@@ -446,10 +458,6 @@ msgctxt "field:cashbook.book,currency_digits:"
 msgid "Currency Digits"
 msgstr "Currency Digits"
 
-msgctxt "field:cashbook.book,start_balance:"
-msgid "Initial Amount"
-msgstr "Initial Amount"
-
 msgctxt "field:cashbook.book,start_date:"
 msgid "Initial Date"
 msgstr "Initial Date"
@@ -482,6 +490,22 @@ msgctxt "help:cashbook.book,number_atcheck:"
 msgid "The numbering of the lines is done in the step Check. If the check mark is inactive, this happens with Done."
 msgstr "The numbering of the lines is done in the step Check. If the check mark is inactive, this happens with Done."
 
+msgctxt "field:cashbook.book,parent:"
+msgid "Parent"
+msgstr "Parent"
+
+msgctxt "field:cashbook.book,childs:"
+msgid "Children"
+msgstr "Children"
+
+msgctxt "field:cashbook.book,left:"
+msgid "Left"
+msgstr "Left"
+
+msgctxt "field:cashbook.book,right:"
+msgid "Right"
+msgstr "Right"
+
 msgctxt "model:cashbook.split,name:"
 msgid "Split booking line"
 msgstr "Split booking line"
diff --git a/menu.xml b/menu.xml
index d4c8a1b..f05d611 100644
--- a/menu.xml
+++ b/menu.xml
@@ -83,9 +83,21 @@ full copyright notices and license terms. -->
         </record>
 
         <!-- menu: /Cashbook/Cashbook -->
+        <menuitem id="menu_booktree" action="act_book_tree"
+            icon="tryton-tree"
+            parent="menu_cashbook" sequence="40"/>
+        <record model="ir.ui.menu-res.group" id="menu_booktree-group_cashbook">
+            <field name="menu" ref="menu_booktree"/>
+            <field name="group" ref="group_cashbook"/>
+        </record>
+        <record model="ir.ui.menu-res.group" id="menu_booktree-group_cashbook_admin">
+            <field name="menu" ref="menu_booktree"/>
+            <field name="group" ref="group_cashbook_admin"/>
+        </record>
+        <!-- menu: /Cashbook/Cashbook/Cashbook -->
         <menuitem id="menu_booklist" action="act_book_view"
             icon="tryton-list"
-            parent="menu_cashbook" sequence="40"/>
+            parent="menu_booktree" sequence="10"/>
         <record model="ir.ui.menu-res.group" id="menu_booklist-group_cashbook">
             <field name="menu" ref="menu_booklist"/>
             <field name="group" ref="group_cashbook"/>
diff --git a/message.xml b/message.xml
index 8fea230..3946a30 100644
--- a/message.xml
+++ b/message.xml
@@ -53,9 +53,6 @@ full copyright notices and license terms. -->
         <record model="ir.message" id="msg_category_type_not_like_parent">
             <field name="text">The type of the current category '%(catname)s' must be equal to the type of the parent category '%(parentname)s'.</field>
         </record>
-        <record model="ir.message" id="msg_book_err_startamount_with_lines">
-            <field name="text">The initial amount of the cash book '%(bookname)s' cannot be changed because it already contains bookings.</field>
-        </record>
         <record model="ir.message" id="msg_line_deny_recon_by_state">
             <field name="text">For reconciliation, the line '%(recname)s' must be in the status 'Check' or 'Done'.</field>
         </record>
diff --git a/reconciliation.py b/reconciliation.py
index 5d19307..efa9e4d 100644
--- a/reconciliation.py
+++ b/reconciliation.py
@@ -226,7 +226,7 @@ class Reconciliation(Workflow, ModelSQL, ModelView):
                         ))
                 values['start_amount'] = reconciliation.predecessor.end_amount
             else :
-                values['start_amount'] = reconciliation.cashbook.start_balance
+                values['start_amount'] = Decimal('0.0')
             values['end_amount'] = values['start_amount']
 
             # add 'checked'-lines to reconciliation
diff --git a/tests/test_book.py b/tests/test_book.py
index 34e5c3e..c5be24e 100644
--- a/tests/test_book.py
+++ b/tests/test_book.py
@@ -51,10 +51,37 @@ class BookTestCase(ModuleTestCase):
             'number_sequ': self.prep_sequence().id,
             }])
         self.assertEqual(book.name, 'Book 1')
+        self.assertEqual(book.rec_name, 'Book 1 | 0.00 usd | Open')
         self.assertEqual(book.btype.rec_name, 'CAS - Cash')
         self.assertEqual(book.state, 'open')
         self.assertEqual(book.state_string, 'Open')
 
+    @with_transaction()
+    def test_book_create_hierarchy(self):
+        """ create cashbook, hierarchical
+        """
+        pool = Pool()
+        Book = pool.get('cashbook.book')
+
+        types = self.prep_type()
+        company = self.prep_company()
+        book, = Book.create([{
+            'name': 'Level 1',
+            'btype': None,
+            'company': company.id,
+            'childs': [('create', [{
+                    'name': 'Level 2',
+                    'btype': types.id,
+                    'company': company.id,
+                    'currency': company.currency.id,
+                    'number_sequ': self.prep_sequence().id,
+                }])],
+            }])
+        self.assertEqual(book.name, 'Level 1')
+        self.assertEqual(book.rec_name, 'Level 1')
+        self.assertEqual(len(book.childs), 1)
+        self.assertEqual(book.childs[0].rec_name, 'Level 1/Level 2 | 0.00 usd | Open')
+
     @with_transaction()
     def test_book_deny_delete_open(self):
         """ create cashbook, add lines, try to delete in state 'open'
@@ -225,62 +252,6 @@ class BookTestCase(ModuleTestCase):
                 },
             ])
 
-    @with_transaction()
-    def test_book_deny_update_start_amount(self):
-        """ create cashbook, add lines, update start-amount
-        """
-        pool = Pool()
-        Book = pool.get('cashbook.book')
-
-        types = self.prep_type()
-        company = self.prep_company()
-        category = self.prep_category(cattype='in')
-        party = self.prep_party()
-        book, = Book.create([{
-            'name': 'Book 1',
-            'btype': types.id,
-            'company': company.id,
-            'currency': company.currency.id,
-            'number_sequ': self.prep_sequence().id,
-            }])
-        self.assertEqual(book.name, 'Book 1')
-        self.assertEqual(book.start_balance, Decimal('0.0'))
-        self.assertEqual(book.rec_name, 'Book 1 | 0.00 usd | Open')
-
-        Book.write(*[
-            [book],
-            {
-                'start_balance': Decimal('1.0'),
-            }])
-        self.assertEqual(book.start_balance, Decimal('1.0'))
-        self.assertEqual(book.balance, Decimal('1.0'))
-
-        Book.write(*[
-            [book],
-            {
-                'lines': [('create', [{
-                    'amount': Decimal('2.0'),
-                    'description': 'Test',
-                    'category': category.id,
-                    'bookingtype': 'in',
-                    'party': party.id,
-                    }])],
-            }])
-        self.assertEqual(book.start_balance, Decimal('1.0'))
-        self.assertEqual(book.balance, Decimal('3.0'))
-        self.assertEqual(len(book.lines), 1)
-        self.assertEqual(book.lines[0].balance, Decimal('3.0'))
-
-        self.assertRaisesRegex(UserError,
-            "The initial amount of the cash book 'Fridas book | 3.00 usd | Open' cannot be changed because it already contains bookings.",
-            Book.write,
-            *[
-                [book],
-                {
-                    'start_balance': Decimal('1.5'),
-                },
-            ])
-
     @with_transaction()
     def test_book_permission_owner(self):
         """ create book + 2x users, add users to group, check access
diff --git a/tests/test_bookingwiz.py b/tests/test_bookingwiz.py
index 29f2665..6a6f1e1 100644
--- a/tests/test_bookingwiz.py
+++ b/tests/test_bookingwiz.py
@@ -39,7 +39,6 @@ class BookingWizardTestCase(ModuleTestCase):
                 'currency': company.currency.id,
                 'number_sequ': self.prep_sequence().id,
                 'start_date': date(2022, 1, 1),
-                'start_balance': Decimal('0.0'),
                 }])
 
             party, = Party.create([{
@@ -114,7 +113,6 @@ class BookingWizardTestCase(ModuleTestCase):
                 'currency': company.currency.id,
                 'number_sequ': self.prep_sequence().id,
                 'start_date': date(2022, 1, 1),
-                'start_balance': Decimal('0.0'),
                 }, {
                 'name': 'Bank',
                 'btype': types.id,
@@ -122,7 +120,6 @@ class BookingWizardTestCase(ModuleTestCase):
                 'currency': company.currency.id,
                 'number_sequ': self.prep_sequence().id,
                 'start_date': date(2022, 1, 1),
-                'start_balance': Decimal('0.0'),
                 }])
 
             party, = Party.create([{
diff --git a/tests/test_line.py b/tests/test_line.py
index 6975fec..450fc9c 100644
--- a/tests/test_line.py
+++ b/tests/test_line.py
@@ -574,6 +574,36 @@ class LineTestCase(ModuleTestCase):
         self.assertEqual(book.lines[2].rec_name, '05/01/2022|Rev/Sp|1.00 usd|Text 3 [-]')
         self.assertEqual(book.lines[2].state, 'edit')
 
+    @with_transaction()
+    def test_line_to_non_type_book(self):
+        """ create cashbook w/o type
+        """
+        pool = Pool()
+        Book = pool.get('cashbook.book')
+        Line = pool.get('cashbook.line')
+
+        category = self.prep_category(cattype='in')
+        company = self.prep_company()
+        party = self.prep_party()
+        book, = Book.create([{
+            'name': 'Book 1',
+            'btype': None,
+            'company': company.id,
+            }])
+        self.assertEqual(book.name, 'Book 1')
+        self.assertEqual(book.state, 'open')
+
+        self.assertRaisesRegex(UserError,
+            'The value for field "Cashbook" in "Cashbook Line" is not valid according to its domain.',
+            Line.create,
+            [{
+                'cashbook': book.id,
+                'date': date(2022, 5, 1),
+                'category': category.id,
+                'bookingtype': 'in',
+                'amount': Decimal('0.0'),
+            }])
+
     @with_transaction()
     def test_line_create_check_deny_write(self):
         """ create cashbook + line, 'close' book, write to line
diff --git a/tests/test_reconciliation.py b/tests/test_reconciliation.py
index f3c8c11..98b77e4 100644
--- a/tests/test_reconciliation.py
+++ b/tests/test_reconciliation.py
@@ -221,7 +221,6 @@ class ReconTestCase(ModuleTestCase):
             'btype': types.id,
             'company': company.id,
             'currency': company.currency.id,
-            'start_balance': Decimal('12.50'),
             'start_date': date(2022, 5, 1),
             'number_sequ': self.prep_sequence().id,
             'reconciliations': [('create', [{
@@ -234,7 +233,7 @@ class ReconTestCase(ModuleTestCase):
         self.assertEqual(book.reconciliations[0].rec_name, '05/01/2022 - 05/31/2022 | 0.00 usd - 0.00 usd [0]')
 
         Reconciliation.wfcheck(list(book.reconciliations))
-        self.assertEqual(book.reconciliations[0].rec_name, '05/01/2022 - 05/31/2022 | 12.50 usd - 12.50 usd [0]')
+        self.assertEqual(book.reconciliations[0].rec_name, '05/01/2022 - 05/31/2022 | 0.00 usd - 0.00 usd [0]')
 
     @with_transaction()
     def test_recon_set_start_amount_by_predecessor(self):
@@ -254,7 +253,6 @@ class ReconTestCase(ModuleTestCase):
             'btype': types.id,
             'company': company.id,
             'currency': company.currency.id,
-            'start_balance': Decimal('12.50'),
             'start_date': date(2022, 5, 1),
             'number_sequ': self.prep_sequence().id,
             'reconciliations': [('create', [{
@@ -287,7 +285,7 @@ class ReconTestCase(ModuleTestCase):
         Reconciliation.wfcheck(list(book.reconciliations))
 
         self.assertEqual(book.reconciliations[0].state, 'check')
-        self.assertEqual(book.reconciliations[0].rec_name, '05/01/2022 - 05/31/2022 | 12.50 usd - 24.50 usd [2]')
+        self.assertEqual(book.reconciliations[0].rec_name, '05/01/2022 - 05/31/2022 | 0.00 usd - 12.00 usd [2]')
         Reconciliation.wfdone(list(book.reconciliations))
         self.assertEqual(book.reconciliations[0].state, 'done')
 
@@ -298,7 +296,7 @@ class ReconTestCase(ModuleTestCase):
             }])
         self.assertEqual(recons[0].rec_name, '05/31/2022 - 06/30/2022 | 0.00 usd - 0.00 usd [0]')
         Reconciliation.wfcheck(recons)
-        self.assertEqual(recons[0].rec_name, '05/31/2022 - 06/30/2022 | 24.50 usd - 24.50 usd [0]')
+        self.assertEqual(recons[0].rec_name, '05/31/2022 - 06/30/2022 | 12.00 usd - 12.00 usd [0]')
 
     @with_transaction()
     def test_recon_predecessor_done(self):
diff --git a/view/book_form.xml b/view/book_form.xml
index 53b925a..c47d19a 100644
--- a/view/book_form.xml
+++ b/view/book_form.xml
@@ -15,29 +15,32 @@ full copyright notices and license terms. -->
         </group>
     </group>
 
+    <label name="btype"/>
+    <field name="btype"/>
     <label name="balance"/>
     <field name="balance"/>
-    <newline/>
 
     <notebook colspan="4">
-        <page id="pgrecon" string="Reconciliations" col="1">
+        <page name="reconciliations" string="Reconciliations" col="1">
             <field name="reconciliations"/>
         </page>
         <page id="pggeneral" string="General Information" col="4">
+            <label name="company"/>
+            <field name="company"/>
+            <label name="parent"/>
+            <field name="parent"/>
+            <field name="childs" colspan="4"/>
+        </page>
+        <page name="number_sequ" string="Amount and Numbering" col="4">
             <label name="number_sequ"/>
             <field name="number_sequ"/>
             <label name="number_atcheck"/>
             <field name="number_atcheck"/>
 
-            <label name="btype"/>
-            <field name="btype"/>
-            <label name="currency"/>
-            <field name="currency"/>
-
-            <label name="start_balance"/>
-            <field name="start_balance"/>
             <label name="start_date"/>
             <field name="start_date"/>
+            <label name="currency"/>
+            <field name="currency"/>
 
             <label id="phaccount" colspan="2" string=" "/>
         </page>
diff --git a/view/book_list.xml b/view/book_list.xml
index 75a290c..bb85e16 100644
--- a/view/book_list.xml
+++ b/view/book_list.xml
@@ -5,7 +5,6 @@ full copyright notices and license terms. -->
 <tree>
     <field name="name"/>
     <field name="btype"/>
-    <field name="start_balance"/>
     <field name="balance" sum="Balance"/>
     <field name="currency"/>
     <field name="owner"/>
diff --git a/view/book_tree.xml b/view/book_tree.xml
new file mode 100644
index 0000000..a09b734
--- /dev/null
+++ b/view/book_tree.xml
@@ -0,0 +1,14 @@
+<?xml version="1.0"?>
+<!-- This file is part of the cashbook-module from m-ds for Tryton.
+The COPYRIGHT file at the top level of this repository contains the
+full copyright notices and license terms. -->
+<tree>
+    <field name="name"/>
+    <field name="btype"/>
+    <field name="balance" sum="Balance"/>
+    <field name="currency"/>
+    <field name="owner"/>
+    <field name="state"/>
+    <field name="parent" tree_invisible="1"/>
+    <field name="childs" tree_invisible="1"/>
+</tree>
diff --git a/view/category_form.xml b/view/category_form.xml
index 9ea7a6e..7a53286 100644
--- a/view/category_form.xml
+++ b/view/category_form.xml
@@ -13,13 +13,12 @@ full copyright notices and license terms. -->
     <field name="description" colspan="5"/>
 
     <notebook colspan="6">
-        <page string="General Information" id="general" col="6">
+        <page string="General Information" id="general" col="4">
             <label name="company"/>
             <field name="company"/>
             <label name="parent"/>
             <field name="parent"/>
-            <newline/>
-            <field name="childs" colspan="6"/>
+            <field name="childs" colspan="4"/>
         </page>
     </notebook>